The use of camera systems in automated welding arose from necessity. Welding in hazardous environments subject to nuclear radiation, vacuums, lasers, argon or water entails the use of welding cameras to remotely control the torch head and wire feed positions as well as to monitor the welding process. Welding cameras provide similar benefits in automated applications with restricted access (including bore cladding, orbital welding and welding at height) or joints subject to preheating. In addition to positioning the torch before and during welding, cameras are used as a real-time post weld inspection tool by positioning the camera for views of the solidifying weld-puddle.

In many of the above cases, welding cameras are applied for monitoring welding of critical joints, expensive materials or in otherwise high value applications such as tube and pipe mills. For these applications, the cost of failure is significant and the ability to take preemptive action is essential. However, the use of welding cameras is not restricted to the most sensitive and expensive welding operations. Advances in camera electronics have improved image quality and reduced purchase price such that welding cameras now prove beneficial to many more automated welding applications. For example, a magnified view of the electrode and torch is useful for improving the set up speed and accuracy of automated micro PAW/TIG, dabber TIG and tube mill applications. The performance of mechanical joint tracking systems is enhanced by camera supervision. Cameras applied to carriages facilitate welding upside down, at height, inside confined spaces and around circumferential joints. Automated systems with multiple weld-torches, like those used to manufacture turbine shafts, welded I-beams, spiral tube and tanks, may be effectively monitored and controlled from a single console.

In addition, we live in an age where welding is increasingly seen as an undesirable vocation. Improving the welders' working conditions is an effective practice towards staff retention. Semi-automatic welding with camera systems enables the welder to relocate away from the bright, hot and smoky welding arc and often cramped conditions. As a result, welding cameras are an effective method for reducing the incidence of accidents and operator’s fatigue. Cameras can also be used to improve the welder’s vision, particularly as eyesight wanes with age, and are especially important for welding applications that require the operator to concentrate on the weld-puddle over long periods of time.

Direct display welding cameras

Direct display (DD) welding cameras are a good fit for applications that benefit from a lower price (such as system that do not need a computer or software), improved reliability as they do not have Windows updates to contend with and/or applications necessitating non-internet / closed-circuit.

MeltTools offer a full range of direct display cameras for all fusion welding processes. The cameras may be customized to fit within the working envelope of the above applications as found on our website or, if not, by contacting us directly. These systems currently use high dynamic range imaging technology (more below).

While the video signal was originally analog, all our systems now use HD-SDI video signal transmission. The HD-SDI video transmission offers low latency, full high-definition resolution (1920x1080) and a great image of the welding scene. They can also be easily converted to low latency transmission systems based on fiber optics, ethernet and wireless for specialist scenarios. Off-the-shelf DVR recording systems offer a very affordable method to troubleshoot production issues.

Commonly DD systems are setup with the interlace transmission mode which makes the video feel fluid. Sometimes a component in the video signal chain requires a progressive scan and so this parameter may be changed. A typical DD system consists of a camera with lighting, cooling, focus and protection mechanisms, a mount, a cable, a controller, a power supply and a display. The controller allows the user to setup the camera, adjust crosshair overlay or temperature readout, and provides the interface for the different inputs and outputs from the camera. A controller may also include video signal conversion, provision for multiple cameras or output for laser pointers. DD systems require little user intervention once setup, automatically adjusting between welding and non-welding. Some customers setup these systems without any provision for changing parameters using the PXCC11 junction box.

The primary use for computer based welding cameras is in applications that automate a control for quality function or advanced data keeping. Typically, the camera output enters the computer by way of GIGE interface as it makes the most sense in industrial applications and does not require additional frame grabbers. However, some of the DD cameras are also setup with computers for advanced AI functions.

Computing welding cameras may be used to enhance human based operations by providing the welder with real-time warnings or controlling an aspect of the process. With automated systems, cameras are used for quality assurance and/or control roles. The primary benefits of increased productivity, accuracy and precision of motion, the ability to adapt to the welding scenario in real-time, a record of work done and automation detection of defects. The image may be interpreted by rules based (machine vision) or artificial intelligence (typically neural networks) and the output used to trigger an alarm or control the welding torch position or welding power source. The image may be manipulated using vision libraries before processing or feed directly into the model. A model may be setup specific to the application it is deployed on or a model may have the ability to interpret a larger range of applications. Please see our blog post for more information on some of the models we build for welding customers.

Most video cameras cannot provide a meaningful image of the melt-zone or wire feed and the background (i.e. joint or solidified weld) during welding because of the incredible brightness of the arc and, to a lesser extent, radiation emitted from the molten weld puddle.

When a scene is too bright for the pixels on the camera’s sensor, the pixels become saturated or white as the sensors well capacity is exceeded. This circumstance corresponds to imaging values of 255 in an 8-bit image and results in a loss of data. At the other end of the scale the is the black level (i.e. towards 0 in an 8-bit image) is where it becomes difficult to distinguish between photons reaching the sensor noise floor.

The relationship between well capacity and the noise floor describes a sensor’s dynamic range. There are many techniques known as high or wide dynamic range imaging that can extend this range from a typical sensor performance of 60-70dB to more than 120 dB. HDR sensors are useful for welding as they can be setup to visualize both the bright arc and melt pool as well as use the reflections from this bright light to image the much darker background. The primary benefit of this approach to weld imaging is found with the small camera sizes and simplicity. As described above, there are some limitations to this method as the lighting of the scene is determined by light emitted and reflected in the welding process with limitations in the field of view as light reflected from the process is required for background illumination. MeltTools offers such systems in both its direct display solutions in both monochrome and color and GIGE and USB3 cameras in monochrome.

More advanced solutions use high intensity laser or LED light sources combined with narrowband filters. With such systems, intense illumination, reflected into the sensor, must be significantly greater from the illumination from the weld-puddle or arc. Light from the process is eliminated. allowing simultaneous visibility of the wire, joint and puddle details. The imaging setup must be carefully considered to ensure that the illumination light acting on the puddle is not reflected to such an extent that the puddle becomes too dark as light can be reflected everywhere except towards the sensor and that the light output does not create a safety hazard.

MeltTools offers pulsed, where the light is synchronized with the camera shutter, and continuous power systems. The pulsed systems are used for our monochrome solutions and is discussed in detail below, while the continuous, found with our RAD8 illumination system, for some specialist color imaging applications.

The major advantages of using controlled pulsed illumination over HDR are that the image tends to be repeatable and clearer, particularly in comparison to HDR methods in circumstances when the welding process may have significant variation in light output (e.g. from aggressive pulse schedules or with variation in lighting from root to capping pass). As such, pulsed illumination cameras form the basis of our artificial intelligence. MeltTools have developed both laser and LED based pulsed illumination systems but mostly offer the former for technical reasons. The main design considerations for our pulsed illumination cameras are a small form factor, capable of working at a range of temperatures and safe for anyone in the region.

Silicon-based sensors cannot convert photons to voltage at wavelengths longer than 1100nm. One major shift in camera technology since MeltTools pioneered the use of high dynamic range imaging in the welding industry 14 years ago is the availability of short-wave infrared (SWIR) sensors and cameras. While more expensive than silicon-based sensors, InGaAS and Quantum Dot technologies now offer high performing imagers in the short-wave infrared range (900-1700nm).

From an understanding of black-body radiation curves we can see that imaging in the SWIR wavelength is advantageous to measuring the temperature profile of a cooling weld and the substrate temperature in three-dimensional printing as well as detecting fusion faults. The MeltView® HT25 is a SWIR camera currently offered that detects thermal changes during the cooling stage of the weld. Care must be taken to ensure that the camera is set up and calibrated for the materials involved and MeltTools offers such services.

MeltTools makes a full range of welding cameras that fit on many different machines and that each have their own set of benefits. Take a look at the table below which summarizes the article in the types of welding cameras there are and the different techniques that can be used to visualize the welding process.

If it is not clear which technology makes the most sense for your applications, reach out to us at sales@melttools.com, fill out our contact us page or book a meeting to chat with our MeltTools team.